The present invention relates to an impact strength modifier which can impart excellent weatherability, particularly fading resistance and impact resistance, and relates to a thermoplastic resin composition containing the same.
This application is based on Japanese Patent Applications Nos. 2000-119879 and 2000-120008, filed in Japan, the content of which is incorporated herein by reference.
As means for improving the impact resistance of commodity thermoplastic resins such as methacrylic resin, polystyrene resin, acrylonitrile/styrene resin and polycarbonate, various publicly known techniques have been proposed.
For example, Japanese Patent Application, Second Publication No. Hei 4-325542B discloses a method of improving the appearance of a product while maintaining its impact resistance by adding a specific alcohol to a rubbery polymer latex. Also, Japanese Patent Application, First Publication No. Hei 10-101869A discloses a method of improving the impact resistance by using a graft copolymer obtained by graft-polymerizing a composite rubber having a structure, wherein an isobutylene polymer segment and a vinyl polymer segment are not mutually separated, with a vinyl monomer.
The vinyl chloride resin is the most versatile resin, but has a drawback such as poor impact resistance. To improve the impact resistance, various methods have been proposed and include, for example, a method of using a MBS resin, which is obtained by graft-polymerizing a butadiene rubbery polymer with methyl methacrylate, styrene or acrylonitrile, in combination with a vinyl chloride resin.
Although the impact resistance is improved by using the MBS resin in combination with the vinyl chloride resin, the weatherability is reduced and, furthermore, the impact resistance is drastically reduced when using the molded article outdoors.
It is believed that the weatherability is mainly reduced by ultraviolet deterioration of a butadiene unit constituting the MBS resin.
Therefore, Japanese Patent Application, Second Publication No. Sho 51-28117B proposes a method of improving the weatherability of the MBS resin and imparting impact resistance by graft-polymerizing a crosslinked alkyl (meth)acrylate rubber polymer comprising an alkyl (meth)acrylate and a crosslinking agent with methyl methacrylate, styrene or acrylonitrile.
However, according to the methods disclosed in Japanese Patent Application, Second Publication No. Hei 4-325542B and Japanese Patent Application, First Publication No. Hei 10-101869A, high impact resistance has never been achieved by improving the impact resistance of commodity thermoplastic resins such as methacrylic resin, polystyrene resin, acrylonitrile/styrene resin and polycarbonate.
According to the method of improving the impact resistance of a vinyl chloride resin using an acrylic graft copolymer disclosed in Japanese Patent Application, Second Publication No. Sho 51-28117B, the resulting molded article is superior in weatherability and reduction of the impact resistance is less likely to occur. However, there arose a problem in that a large amount of the acrylic graft copolymer must be added to yield the impact strength and the acrylic graft copolymer is inferior in the impact resistance-manifesting effect, particularly the impact resistance-manifesting effect at low temperature to the MBS resin.
An object of the present invention is to provide an impact strength modifier which can improve the impact resistance, particularly low-temperature impact resistance of the resin by adding it in a small amount and can satisfactorily maintain the weatherability such as fading resistance or impact resistance of the resulting molded article, and thermoplastic resin composition containing the same.
The impact strength modifier of the present invention comprises an acrylic rubber graft copolymer (I) obtained by graft-polymerizing a polyalkyl (meth)acrylate composite rubber (A) with a vinyl monomer (B), and a compound (II) which has a sulfonic acid group or a sulfuric acid group and also has two or more benzene ring skeletons, or a salt thereof, wherein the polyalkyl (meth)acrylate composite rubber (A) contains two or more acrylic rubber components each having a different glass transition temperature, and the respective acrylic rubber components have 20% by weight or less of a monomer having two or more unsaturated bonds in a molecule.
The impact strength modifier of the present invention comprises an acrylic rubber graft copolymer (I) obtained by graft-polymerizing a polyalkyl (meth)acrylate composite rubber (A) with a vinyl monomer (B), and a compound (II) which has a sulfonic acid group or a sulfuric acid group and also has two or more benzene ring skeletons, or a salt thereof, wherein the polyalkyl (meth)acrylate composite rubber (A) contains two or more acrylic rubber components each having a different glass transition temperature, the respective acrylic rubber components have 20% by weight or less of a monomer having two or more unsaturated bonds in a molecule, and a particle size distribution of the polyalkyl (meth)acrylate composite rubber (A) is a polydisperse distribution in which at least one peak exists within a range from 0.05 to 0.4 xcexcm and a weight percentage within the range is from 50 to 99.9% by weight, and at least one peak exists within a range from 0.4 to 1.0 xcexcm and a weight percentage within the range is from 0.1 to 50% by weight.